Fungicides play an important role in; agriculture, because without their use a considerable part of vegetable, fruit, cereals and flowers crop would be lost every year. The disinfection of all kinds of buildings, containers and tools require also the application of fungicides to avoid disease, moulds growing, contamination of foods and so on. On the other hand, in view of the specificity of most of the known fungicidal substances, and in view of the great number of existing fungi, it is not surprising that hundreds of various fungicides are commercially available. Generally speaking each of the commercial products has utility in a certain field and to a certain extent: that means almost each product is suitable for killing certain species of moulds, on certain plants or materials, and in certain conditions of temperature, light, humidity etc. Nevertheless, much is still to be improved, particularly as concerns toxicity, phytotoxicity, biodegradability, staining and killing some very virulent widespread germs.
In the course of last 20 years, attractive attempts have been made to improve the fungicidal action of copper. As known, copper compounds have been used with success, particularly in the protection of vine against mildew, for almost a century; however, as the composition must be substantially neutral, it bears copper in the form of hydroxide, basic sulfate, oxychloride or similar water insoluble material; the slurry, such as the known Bordeaux mixture, sprayed onto the plants must have a rather high content in Cu, generally about 5 g Cu per liter, to be effective. Thus considerable amounts of copper are sprayed every year onto fields and some of the insoluble compound remains stuck to fruit. The improvement, which has been proposed by several authors since 1955, consists in using copper in/the form of its complexes with amines. Since numerous of the complexes being water soluble and highly active against fungi, they are effective in much lower dose than are the old insoluble compounds.
Thus, French Pat. No. 1,130,117 suggests on page 2, lines 1-10, the use of metal complexes of polyamines such as lauryl-ethylene-diamine or tetraethylene-pentamine. U.S. Pat. No. 2,924,551 teaches the application of fungicides constituted by copper or other heavy metals complexes with diamines R'R'N(CH.sub.2).sub.n NRR', where R is an aliphatic hydrocarbon C.sub.8 to C.sub.20 radical, n is 2 to 5, and R' is methyl or H, at least one of the R' present being H. According to French Pat. No. 1,301,904, the complexes of the above U.S. Patent are too phytotoxic and should be replaced by complexes derived from the particular polyamines represented by the formula: EQU RNH(CH.sub.2).sub.3 NH(CH.sub.2).sub.3 NHR'
where R is a C.sub.6 to C.sub.22 aliphatic hydrocarbyl, while R' is H or a group --CH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2.
U.S. Pat. No. 2,977,279 discloses fungicides formed by copper complexes with N-alkenyl-alkylene-polyamines having 3 to 5 amino groups separated by --CH.sub.2 CH.sub.2 -- or --CH.sub.2 CH.sub.2 CH.sub.2 -- chains; the alkenyl radical on N has 8 to 18 C atoms.
As a matter of fact, most of the above amino-copper complexes are quite active anticryptogamic agents and several of them strongly kill various fungi. Their use results in a very substantial sparing of copper, as solutions having 0.2 to 0.5 g Cu per liter are at least as effective as conventional copper compounds slurries with 5 g Cu/l, while amino-copper complex solutions of 0.5 to 1 g Cu/l are much more active than the slurries. The question arises why the copper amino complexes have had no commercial success until now. It seems the answer to this question is found in the third paragraph of page 1 of the above mentioned French Pat. No. 1,301,904, which points out the phytotoxicity of the complexes disclosed in U.S. Pat. No. 2,924,551. Thorough experiences showed that, in fact, not only were the complexes of U.S. Pat. No. 2,924,551 were too much dangerous in practice, but also those of the other prior art cited, including those of the French Pat. No. 1,301,904 itself.
To best understand the matter it will be useful to consider Table I, columns 5 and 6, of the U.S. Pat. No. 2,924,551. It is true that the lethal doses LD.sub.50 of the Cu complexes concerned, versus the studied fungi are 0.6 to 14.0 ppm. as shown in the 6th vertical column of the Table, when determined in vitro by the "Standard Fungicidal Test" of Am. Phys. Soc. It is also true the minimal phytotoxic dosage on tomato or pepper, in certain particular conditions, may be 2,000 ppm. However, in field experience to obtain significant results one must spray a solution or emulsion of amine Cu complex at a concentration of at least 1000 ppm. and often even as high as about 3000 ppm. This practice is the same as with all conventional fungicides. For instance, it is known that according to the Standard Fungicidal Test maneb (manganese ethylene-bis-dithiocarbamate) exerts a fungistatic action at a dosage of about 10 ppm; nevertheless in practice concentrations of 1000 to 2800 ppm are recommended in producers pamphlets as well as in phytotechnical literature ("Chemical and Natural Control of Pests" -- E. R. de ONG -- Reihold Publishing Corp. -- 1960; page 134 second paragraph: 2 pounds of 70% maneb per 100 gallons i.e. 1670 ppm.). That means when the Cu complexes are used in practice, the necessary concentration is of the same order of magnitude as the minimal phytotoxic dosage. Then it is not surprising that risks of damage to plants occur.
On the other hand, the sensitivity of different vegetals to chemical compounds strongly varies with the specie of plant, age, temperature, air humidity, intensity of light etc. It is not possible to generally characterize the phytotoxicity of a compound by tests on one or two plants. While tomato or pepper may resist, for example, 1500 ppm of a Cu-amine complex, grape or vetch can be less or more severely attacked. That is the reason for which the toxicity to plants of the compositions according to the present invention was tested on a great number of various plants, in summer, under several hours of sunning per day, and average statistical data were drawn from the tests.